What is Genetic Diagnosis? Unveiling Insights into Your Health

Genetic diagnosis, often referred to as genetic testing, is a powerful medical tool that involves examining your DNA. DNA, or deoxyribonucleic acid, serves as the fundamental chemical database within our cells, containing the intricate instructions necessary for our bodies to function correctly. This examination can reveal alterations, known as mutations, in your genes that might be the root cause of, or increase your susceptibility to, various illnesses and diseases.

While genetic diagnosis offers invaluable insights for diagnosing, managing, treating, and even preventing diseases, it’s essential to understand its limitations. For instance, a positive result in a healthy individual doesn’t definitively mean disease development is inevitable. Conversely, a negative result doesn’t always rule out the possibility of having a specific condition. Therefore, a crucial step in the genetic testing journey is consulting with a healthcare professional – be it your doctor, a medical geneticist, or a genetic counselor – to thoroughly discuss the implications and potential actions based on the test results.

Delving Deeper: Genome Sequencing

In situations where standard genetic testing doesn’t pinpoint a diagnosis, yet a genetic cause is strongly suspected, advanced facilities may offer genome sequencing. This sophisticated process involves a comprehensive analysis of a DNA sample, typically extracted from your blood.

Every individual possesses a unique genome, which is the complete set of DNA encompassing all of a person’s genes. Genome sequencing is a complex analysis designed to identify genetic variations that could be linked to your health. Often, this in-depth testing focuses on the exome, which comprises the protein-encoding regions of DNA.

Why is Genetic Diagnosis Performed?

Genetic diagnosis plays a critical role in various aspects of healthcare, from assessing the risk of developing specific diseases to guiding screening strategies and informing medical treatment decisions. Different types of genetic tests are employed for distinct purposes:

Diagnostic Genetic Diagnosis: If you are experiencing symptoms suggestive of a disease that may stem from genetic changes, diagnostic genetic testing can confirm whether you have the suspected condition. For example, it is instrumental in confirming diagnoses like cystic fibrosis or Huntington’s disease.
Presymptomatic and Predictive Genetic Diagnosis: If you have a family history burdened by a genetic condition, undergoing genetic testing before symptoms appear can reveal your risk of developing that condition. This is particularly useful in assessing your predisposition to certain cancers, such as types of colorectal cancer.
Carrier Genetic Diagnosis: If you or your partner have a family history of a genetic disorder like sickle cell anemia or cystic fibrosis, or if you belong to an ethnic group with a higher prevalence of specific genetic disorders, carrier genetic testing can be invaluable before starting a family. Expanded carrier screening can detect genes associated with a wide array of genetic diseases and mutations, determining if you and your partner are carriers for the same conditions.
Pharmacogenetic Diagnosis: For individuals already diagnosed with a health condition, pharmacogenetic testing can help tailor treatment plans. This type of genetic diagnosis can predict how you might respond to different medications and dosages, optimizing treatment effectiveness and minimizing adverse effects.
Prenatal Genetic Diagnosis: Expectant parents can utilize prenatal tests to screen for certain genetic abnormalities in their developing baby. Down syndrome and trisomy 18 syndrome are commonly screened for using prenatal genetic diagnosis. Traditional methods involve analyzing markers in maternal blood or invasive procedures like amniocentesis. More recently, cell-free DNA testing has emerged, analyzing fetal DNA from a maternal blood sample.
Newborn Screening: This is perhaps the most widespread application of genetic diagnosis. In the United States, newborn screening for specific genetic and metabolic abnormalities is mandatory. Early detection through newborn screening is crucial because it allows for timely intervention and treatment for conditions like congenital hypothyroidism, sickle cell disease, or phenylketonuria (PKU), significantly improving outcomes.
Preimplantation Genetic Diagnosis: Also known as preimplantation genetic testing, this specialized form of genetic diagnosis is used in conjunction with in vitro fertilization (IVF). Embryos created during IVF are screened for genetic abnormalities before implantation, increasing the chances of a healthy pregnancy.

Potential Risks Associated with Genetic Diagnosis

Generally, genetic tests pose minimal physical risk. Standard procedures like blood draws and cheek swabs are virtually risk-free. However, prenatal invasive tests such as amniocentesis or chorionic villus sampling carry a slight risk of pregnancy loss.

Beyond physical risks, genetic diagnosis can also present emotional, social, and financial challenges. It is vital to have a comprehensive discussion about all potential risks and benefits with your doctor, a medical geneticist, or a genetic counselor before undergoing any genetic test.

Preparing for Genetic Diagnosis

Prior to undergoing genetic diagnosis, it is beneficial to gather extensive information about your family’s medical history. Then, consult with your physician or a genetic counselor to discuss your personal and family medical history in detail to gain a clearer understanding of your individual risk factors. Don’t hesitate to ask questions and voice any concerns you may have about genetic testing during this consultation. Furthermore, discuss potential options and implications based on various test result scenarios.

If you are considering testing for a genetic disorder with a familial pattern, it may be helpful to discuss your decision with family members. Pre-test conversations can provide insight into how your family might react to your results and the potential impact on family dynamics.

It’s also important to be aware that health insurance coverage for genetic testing can vary. Before proceeding with a test, verify with your insurance provider to understand the extent of your coverage.

In the United States, the Genetic Information Nondiscrimination Act of 2008 (GINA) offers legal protection against discrimination by health insurers or employers based on genetic test results. GINA prohibits employment discrimination based on genetic predisposition. However, it’s important to note that GINA does not extend to life, long-term care, or disability insurance. Many states offer additional layers of protection.

What to Expect During the Genetic Diagnosis Process

The process of genetic diagnosis involves collecting a sample of your blood, skin, amniotic fluid, or other tissue, depending on the type of test. The sample is then sent to a specialized laboratory for analysis.

Blood Sample: A healthcare professional will draw a blood sample by inserting a needle into a vein in your arm. For newborn screening, a small blood sample is collected via a heel prick.
Cheek Swab: Some genetic tests can be performed using a cheek swab, where a swab is gently rubbed against the inside of your cheek to collect cells.
Amniocentesis: This prenatal test involves inserting a thin needle through the abdominal wall into the uterus to collect a small amount of amniotic fluid.
Chorionic Villus Sampling (CVS): Another prenatal test, CVS involves taking a tissue sample from the placenta, either through the cervix using a catheter or through the abdominal wall and uterus using a thin needle.

Understanding Genetic Diagnosis Results

The timeframe for receiving genetic test results can vary depending on the test type and the healthcare facility. Discuss result timelines with your doctor, medical geneticist, or genetic counselor before the test, and schedule a follow-up appointment to discuss the results in detail.

Interpreting Positive Results

A positive genetic test result indicates that the genetic change being tested for was detected. The subsequent steps depend heavily on the reason for undergoing genetic diagnosis.

If the test was to:

Diagnose a specific disease: A positive result aids in confirming the diagnosis and guides you and your doctor in formulating an appropriate treatment and management plan.
Assess carrier status: If you are found to be a carrier of a gene that could cause disease in your child, your healthcare team can help assess your child’s risk of developing the disease and provide information for family planning decisions.
Predict disease risk: A positive result indicating an increased risk of developing a certain disease does not guarantee disease onset. For example, carrying a breast cancer gene (BRCA1 or BRCA2) signifies a higher risk of breast cancer, but not a certainty. However, in conditions like Huntington’s disease, a positive result for the altered gene is indicative of eventual disease development.

Discuss the specific implications of a positive result with your doctor. Lifestyle modifications may be possible to mitigate disease risk, even with a predisposing gene. Results also inform decisions regarding treatment, family planning, career choices, and insurance coverage. Participation in research or registries related to your condition can also keep you informed about advancements in prevention and treatment.

Interpreting Negative Results

A negative result means the specific mutated gene being tested for was not detected. While reassuring, it’s not a complete guarantee that you will not develop the disorder. The accuracy of genetic tests varies by condition and whether the specific mutation was previously identified in a family member.

Even without the detected mutated gene, the possibility of developing the disease remains. For instance, most individuals who develop breast cancer do not carry BRCA1 or BRCA2 genes. Furthermore, genetic testing may not detect all possible genetic defects.

Interpreting Inconclusive Results

In some instances, genetic tests yield inconclusive results, providing unclear information about the gene in question. Genetic variations are common, and many are harmless. However, distinguishing between a disease-causing variation and a benign one can be challenging. These ambiguous changes are termed variants of uncertain significance. Follow-up testing or periodic gene reviews over time may be necessary in such cases.

The Role of Genetic Counseling

Regardless of the outcome of your genetic diagnosis, genetic counseling is invaluable. Consult with your doctor, medical geneticist, or a genetic counselor to address any questions or concerns. They will help you understand the results’ implications for you and your family, ensuring informed decision-making.

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References

National Library of Medicine. Help me understand genetics. Genetics Home Reference. https://ghr.nlm.nih.gov/primer. Accessed Feb. 13, 2017.
Frequently asked questions about genetic testing. National Human Genome Research Institute. https://www.genome.gov/19516567/faq-about-genetic-testing/. Accessed Feb. 13, 2017.
Genetic testing for hereditary cancer syndromes. National Cancer Institute. https://www.cancer.gov/about-cancer/causes-prevention/genetics/genetic-testing-fact-sheet. Accessed Feb. 13, 2017.
Raby BA, et al. Genetic testing. http://www.uptodate.com/home. Accessed Feb. 13, 2017.
Grody WW, et al. ACMG position statement on prenatal/preconception expanded carrier screening. Genetics in Medicine. 2013;15:482.
Genetic testing. American Medical Association. https://www.ama-assn.org/content/genetic-testing. Accessed Feb. 13, 2017.
Frequently asked questions. Prenatal genetic diagnostic tests. FAQ164. Pregnancy. American College of Obstetricians and Gynecologists. https://www.acog.org/-/media/For-Patients/faq164.pdf?dmc=1&ts=20161216T1208042192. Accessed Feb. 13, 2017.
Breast cancer risk factors you cannot change. American Cancer Society. https://www.cancer.org/cancer/breast-cancer/risk-and-prevention/breast-cancer-risk-factors-you-cannot-change.html. Accessed Feb. 21, 2017.
Atwal PS (expert opinion). Mayo Clinic, Jacksonville, Fla. Feb. 24, 2017.